There has been concern for a long time regarding the fabric materials utilized to coat chairs, beds and other articles which contain polyurethane foam cushioning from the standpoint of the flame retardancy or fire resistance of the overall construction. The polyurethane foam produced for use in such materials can be made flame retardant, but this generally requires the use of very expensive additives which also are harmful to form aesthetic properties (e.g. CMHR foam). Neoprene foams also can be used for flame retardancy, but they are very expensive and dense. A chart listing the approximate density and cost for different types of foams appears below.
______________________________________ Density Cost Material (lbs./cu.ft.) (.cent./bd.ft.) ______________________________________ Non-flame retardant foam l to 2.5 12-15 California HR-117* foam 1.5 to 3 19-25 Melamine Modified Foam (MPU) 3-4 57-62 Combustion Modified HR Foam (CMHR) 4-5 70-80 Neoprene Foam 6-8 90-95 ______________________________________ *High Resiliency Foam in conformance with State of California Technical Bulletin 117 entitled "Requirements, Test Procedure and Apparatus for Testing the Flame Retardance of Resilient Filling Materials used in Upholstered Furniture.
These foams generally reflect different levels of flame retardance, with the Neoprene foam providing the highest level of flame retardance, followed by the CMHR, MPU and HR-117 foams. The relative flame retardance of the foam is directly proportional to its cost, but the physical properties of the foam, particularly the compression set, tensile strength and toughness properties, are generally inversely proportional to the flame retardance levels of the foam. Thus, furniture manufacturers prefer to utilize the HR-117 and MPU foams due to their low cost and improved physical properties. The flame retardancy of the latter materials, however, is insufficient to pass certain stringent fire codes and standards.
Despite their utility as flame retardant materials, each of these foams will burn in the presence of a flame, the extent of the burning being directly dependent upon the duration and amount of heat to which the foam is exposed from fire or a flame. Accordingly, it is generally accepted in the industry to protect the foam from such exposure to flame by the use of a material which acts as a barrier to the flame, especially when protection against intense flame exposure is desired.
The types of barriers which have been used according to the prior art include flame-retardant fabrics, batting or foams. Many of these are effective in protecting foams used in cushions from exposure to flame. However, they result in additional steps in the furniture manufacturing process, adding cost. They also often reduce product aesthetics. As discussed below, the current invention overcomes both of these disadvantages.
Another problem which must be addressed is the fact that many coated fabrics and foams, when tested individually, provide flame retardance properties which are acceptable by many standards. When combined in a chair or similar article, however, the combination of such materials provides insufficient flame retardance. Furthermore, many regulations set relatively low standards which almost any type of flame retardant material can pass. This may lead certain manufacturers to use lesser cost foams which, as noted above, possess a lesser degree of flame retardancy. The same is true for the use of lesser cost coated fabrics.
The challenge, therefore, is to develop a coated fabric for use on a foam, cushion or support to achieve a combination which is capable of self-extinguishing after a flame is removed without burning excessively, exposing the foam to the flame, or generating large quantities of smoke or other toxic gases.
Generally, coated fabrics include a layered structure usually of four or five layers. A top coat, usually less than 1 mil thickness, is used for abrasive resistance and surface wear. This tough layer can be formulated of a PVC/acrylic, urethane or other acrylic composition, and it also imparts a luster or gloss finish to the article. Next, a PVC skin coat of about 5 to 10 mils is used for color and snag resistance. If needed, a color correction layer can be applied between the top and skin coats. Beneath the skin coat is often a PVC foam layer of between about 15 and 40 mils. A PVC adhesive can be used to ensure good bonding between the coating and the fabric backing, which normally is a natural or synthetic fiber or combinations thereof in a knit, woven, or other configuration. The particular fabric construction is selected based on the end use of the coated fabric, with consideration given to the requirements of hand, tailorability, drapability, etc.
Such coated fabrics have been on the market for a long time due to the relative ease of combining these materials into a composite structure. As noted above, however, the PVC layers will burn in the presence of a flame. Should enough heat and flame be encountered to burn a significant portion of the PVC material, the fabric will open and allow the fire to attack the foam. Even when the highest flame retardancy foam formulations are used, flame in contact with the foam can cause burning which generates large quantities of smoke and other toxic gases. In addition, use of such highly flame retardant foam incurs a much greater cost for the construction of the chair or other article, while also producing less comfortable seating. Thus, it is important to achieve a construction wherein the foam does not become exposed to the flame due to opening of the fabric when the coating burns.
It is well known that fiberglass fabric does not burn, hence, a wide variety of single strand, mat, and woven fiberglass fabrics have been used as backings for PVC coatings. Various combinations of knit and woven fiberglass fabrics have been utilized in an attempt to develop a fabric backing which will not open up and expose the foam to flame. In addition to high costs, these materials are deficient with respect to the aesthetics of the coated fabric, i.e., the "feel" of the fabric as well as other features such as flexibility, sewability, tailorability, drapability, manufacturability and the like. Accordingly, there is a great need in the trade for a coated fabric product which possesses the desired flame retardant capabilities as well as aesthetic properties for use on chairs, couches, automobile seats and the like. The present invention provides one such construction, as will be explained in detail hereinbelow.